Vernal Pools

Vernal pools are temporary bodies of water that flood each year for a few months during the spring and early summer. Vernal, or "spring" pools fill up with melting snow and early rains, then usually dry up by mid to late summer. Some relatively deep pools may remain flooded for a few years but become completely dry in seasons with very low rainfall. Autumnal pools fill during the fall with increasing rainfall.

Presently, WPC zoologist Ryan Evans is conducting research on vernal pool ecology at a site in Centre County. He is sampling and describing the animal life inhabiting these wetlands to see how widely the communities differ.

Because vernal pools are not permanently flooded, they do not support fish populations and thus provide safe breeding sites for several amphibians and many invertebrate species, including wood frogs, spotted salamanders and fairy shrimp. These species have evolved life cycles that depend on temporary pools. Suitable pools must have enough leaf litter and other debris to provide food sources and cover for the species that breed in them.

Vernal pools vary in size, ranging from several square feet to an acre. They can be found in a variety of sites, such as isolated depressions in the woods, kettle holes, and gravel pits. Many are within larger wetlands, such as oxbows in river floodplains and pools in forested swamps or scrub-shrub wetlands.

The above photo was taken at Scotia Barrens (State Gamelands No. 176) in Centre County.

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